As someone clearing the Balance of Power quest chain on 12 characters, over half of the normal runs I've been in have either failed in Nighthold terribly, or contained extremely aggressive players belittling anyone who is underperforming in a way you don't usually get in LFR.
And when I say underperforming, I mean capable of helping to kill a boss, but not pulling leet DPS above what's required. If a group wipes once, chances are high the group falls apart, or the lower DPS get kicked.
Even normal is a stressful environment for non-serious raiders.